Configure Redis for a deployment

Configure Redis for a deployment#

This guide shows you how to point Plone at a Redis server and run that server the way a shared cache needs.

Set the URL#

Set REDIS_MEMOIZE_URL in the environment of every Plone instance:

REDIS_MEMOIZE_URL=redis://redis:6379/0

The URL accepts the redis://, rediss:// (TLS), and unix:// schemes, as redis-py does. Put a password in it when the server requires one: redis://:secret@redis:6379/0. The status endpoint and the logs never show the password.

Give every instance of one site the same URL and the same REDIS_MEMOIZE_PREFIX. Give different sites, or different stacks sharing one server, different prefixes.

Configuration lists every variable. Plone reads them once, at startup, and refuses to start when one is invalid, naming the variable.

Run Redis as a cache#

A cache holds nothing worth keeping across a restart, and must never fill the server's memory. Start Redis with persistence off and a memory limit, evicting the least recently used keys:

  • --save '' and --appendonly no turn persistence off;

  • --maxmemory sets the limit;

  • --maxmemory-policy allkeys-lru makes Redis evict old values instead of refusing new ones.

Keep it on a private network#

Only the Plone instances need to reach Redis. In Docker Compose or Swarm, put Redis on an internal network, publish no port, and connect the backend to that network:

services:
  backend:
    image: plone/server-prod-config:6.2
    environment:
      REDIS_MEMOIZE_URL: redis://redis:6379/0
      REDIS_MEMOIZE_PREFIX: example-org
    networks:
      - cache
      - default
    deploy:
      replicas: 2

  redis:
    image: redis:7-alpine
    command:
      - redis-server
      - --save
      - ''
      - --appendonly
      - 'no'
      - --maxmemory
      - 256mb
      - --maxmemory-policy
      - allkeys-lru
    networks:
      - cache

networks:
  cache:
    internal: true

The test suite parses this file and checks each of these properties.

If anything else shares the network, add --requirepass to the Redis command and the password to the URL, or use TLS with rediss://. Security model explains why this matters.

Check it#

Request the status endpoint as a Manager on any instance. active is true, server.version shows the Redis version, and breaker.open is false.

Next steps#

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